The French government is now investigating Guy Wildenstein, the New York and Paris-based scion of the family of art dealers, over allegations that he hid billions of euros around the globe.

For years, Wildenstein's stepmother, Sylvia Roth, who died in 2010, accused Wildenstein of concealing a large portion of his father's estate in offshore trusts from Ireland to the Cayman Islands. Last week, investigators began to look into charges of breach of trust and money laundering.

One source estimates that Wildenstein's fortune may be worth about €4 billion ($5.5 billion).

Roth's suit is continuing against Wildenstein through her lawyer and is now joined by the government's case,

In a separate case, Wildenstein was charged earlier this year with possession of stolen goods and breach of trust. During an investigation into Roth's claims, police found artworks by the likes of Berthe Morisot, Edgar Degas, and Rembrandt Bugatti that had been missing from collectors' estates in the vault of the Wildenstein Institute in Paris.

Several lawsuits are pending against Wildenstein. One dispute involves "The Lute Player," a £69 million painting by Caravaggio, held in the Metropolitan Museum of Art in New York with the title “from a private collection,” according to the Telegraph.